DPDK patches and discussions
 help / color / mirror / Atom feed
From: "Burakov, Anatoly" <anatoly.burakov@intel.com>
To: David Christensen <drc@linux.vnet.ibm.com>, david.marchand@redhat.com
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v3 1/1] vfio: modify spapr iommu support to use static window sizing
Date: Thu, 8 Oct 2020 10:39:33 +0100
Message-ID: <03bace21-0a55-e88b-7f13-2a8764125547@intel.com> (raw)
In-Reply-To: <f3fe2cef-70fa-3cac-73b3-64e21305de15@linux.vnet.ibm.com>

On 07-Oct-20 6:44 PM, David Christensen wrote:
> 
> 
> On 9/17/20 4:13 AM, Burakov, Anatoly wrote:
>> On 10-Aug-20 10:07 PM, David Christensen wrote:
>>> The SPAPR IOMMU requires that a DMA window size be defined before memory
>>> can be mapped for DMA. Current code dynamically modifies the DMA window
>>> size in response to every new memory allocation which is potentially
>>> dangerous because all existing mappings need to be unmapped/remapped in
>>> order to resize the DMA window, leaving hardware holding IOVA addresses
>>> that are temporarily unmapped.  The new SPAPR code statically assigns
>>> the DMA window size on first use, using the largest physical memory
>>> memory address when IOVA=PA and the highest existing memseg virtual
>>> address when IOVA=VA.
>>>
>>> Signed-off-by: David Christensen <drc@linux.vnet.ibm.com>
>>> ---
>>
>> <snip>
>>
>>> +struct spapr_size_walk_param {
>>> +    uint64_t max_va;
>>> +    uint64_t page_sz;
>>> +    int external;
>>> +};
>>> +
>>> +/*
>>> + * In order to set the DMA window size required for the SPAPR IOMMU
>>> + * we need to walk the existing virtual memory allocations as well as
>>> + * find the hugepage size used.
>>> + */
>>>   static int
>>> -vfio_spapr_unmap_walk(const struct rte_memseg_list *msl,
>>> -        const struct rte_memseg *ms, void *arg)
>>> +vfio_spapr_size_walk(const struct rte_memseg_list *msl, void *arg)
>>>   {
>>> -    int *vfio_container_fd = arg;
>>> +    struct spapr_size_walk_param *param = arg;
>>> +    uint64_t max = (uint64_t) msl->base_va + (uint64_t) msl->len;
>>> -    /* skip external memory that isn't a heap */
>>> -    if (msl->external && !msl->heap)
>>> -        return 0;
>>> +    if (msl->external) {
>>> +        param->external++;
>>> +        if (!msl->heap)
>>> +            return 0;
>>> +    }
>>
>> It would be nice to have some comments in the code explaining what 
>> we're skipping and why.
> 
> Reviewing this again, my inclination is to skip ALL external memory, 
> which by definition would seem to be outside of IOMMU control, so the 
> code would read:
> 
>     if (msl->external) {
>         param->external++;
>         return 0;
>     }

The external memory can still be mapped for DMA with rte_dev_dma_map() 
API. The heap memory is meant to be mapped automatically by DPDK, while 
the non-heap memory (created with rte_extmem_register() API) is meant to 
be managed by the user and will be mapped using the user_mem_map 
functions in this file.

> 
> Not sure why existing code such as vfio_spapr_map_walk() distinguishes 
> between heap and non-heap in this situation.  Are there instances in x86 
> where it would matter?
> 
>> Also, seems that you're using param->external as bool? This is a 
>> non-public API so using stdbool is not an issue here, perhaps replace 
>> it with bool param->has_external?
> 
> Why do you think the distinction is necessary?
> 

It's not *necessary*, i just don't like the ancient C style where ints 
are used as booleans :D Not a serious issue though, your choice.

> Dave


-- 
Thanks,
Anatoly

  reply	other threads:[~2020-10-08  9:39 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-29 23:29 [dpdk-dev] [PATCH 0/2] vfio: change spapr DMA window sizing operation David Christensen
2020-04-29 23:29 ` [dpdk-dev] [PATCH 1/2] vfio: use ifdef's for ppc64 spapr code David Christensen
2020-04-30 11:14   ` Burakov, Anatoly
2020-04-30 16:22     ` David Christensen
2020-04-30 16:24       ` Burakov, Anatoly
2020-04-30 17:38         ` David Christensen
2020-05-01  8:49           ` Burakov, Anatoly
2020-04-29 23:29 ` [dpdk-dev] [PATCH 2/2] vfio: modify spapr iommu support to use static window sizing David Christensen
2020-04-30 11:34   ` Burakov, Anatoly
2020-04-30 17:36     ` David Christensen
2020-05-01  9:06       ` Burakov, Anatoly
2020-05-01 16:48         ` David Christensen
2020-05-05 14:57           ` Burakov, Anatoly
2020-05-05 16:26             ` David Christensen
2020-05-06 10:18               ` Burakov, Anatoly
2020-06-30 21:38 ` [dpdk-dev] [PATCH v2 0/1] vfio: change spapr DMA window sizing operation David Christensen
2020-06-30 21:38   ` [dpdk-dev] [PATCH v2 1/1] vfio: modify spapr iommu support to use static window sizing David Christensen
2020-08-10 21:07   ` [dpdk-dev] [PATCH v3 0/1] vfio: change spapr DMA window sizing operation David Christensen
2020-08-10 21:07     ` [dpdk-dev] [PATCH v3 1/1] vfio: modify spapr iommu support to use static window sizing David Christensen
2020-09-03 18:55       ` David Christensen
2020-09-17 11:13       ` Burakov, Anatoly
2020-10-07 12:49         ` Thomas Monjalon
2020-10-07 17:44         ` David Christensen
2020-10-08  9:39           ` Burakov, Anatoly [this message]
2020-10-12 19:19             ` David Christensen
2020-10-14  9:27               ` Burakov, Anatoly
2020-10-15 17:23     ` [dpdk-dev] [PATCH v4 0/1] vfio: change spapr DMA window sizing operation David Christensen
2020-10-15 17:23       ` [dpdk-dev] [PATCH v4 1/1] vfio: modify spapr iommu support to use static window sizing David Christensen
2020-10-20 12:05         ` Thomas Monjalon
2020-10-29 21:30           ` Thomas Monjalon
2020-11-02 11:04         ` Burakov, Anatoly
2020-11-03 22:05       ` [dpdk-dev] [PATCH v5 0/1] " David Christensen
2020-11-03 22:05         ` [dpdk-dev] [PATCH v5 1/1] " David Christensen
2020-11-04 19:43           ` Thomas Monjalon
2020-11-04 21:00             ` David Christensen
2020-11-04 21:02               ` Thomas Monjalon
2020-11-04 22:25                 ` David Christensen
2020-11-05  7:12                   ` Thomas Monjalon
2020-11-06 22:16                     ` David Christensen
2020-11-07  9:58                       ` Thomas Monjalon
2020-11-09 20:35         ` [dpdk-dev] [PATCH v5 0/1] " David Christensen
2020-11-09 20:35           ` [dpdk-dev] [PATCH v6 1/1] " David Christensen
2020-11-09 21:10             ` Thomas Monjalon
2020-11-10 17:41           ` [dpdk-dev] [PATCH v7 0/1] " David Christensen
2020-11-10 17:41             ` [dpdk-dev] [PATCH v7 1/1] " David Christensen
2020-11-10 17:43           ` [dpdk-dev] [PATCH v7 0/1] " David Christensen
2020-11-10 17:43             ` [dpdk-dev] [PATCH v7 1/1] " David Christensen
2020-11-13  8:39               ` Thomas Monjalon

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=03bace21-0a55-e88b-7f13-2a8764125547@intel.com \
    --to=anatoly.burakov@intel.com \
    --cc=david.marchand@redhat.com \
    --cc=dev@dpdk.org \
    --cc=drc@linux.vnet.ibm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

DPDK patches and discussions

This inbox may be cloned and mirrored by anyone:

	git clone --mirror https://inbox.dpdk.org/dev/0 dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dev dev/ https://inbox.dpdk.org/dev \
		dev@dpdk.org
	public-inbox-index dev

Example config snippet for mirrors.
Newsgroup available over NNTP:
	nntp://inbox.dpdk.org/inbox.dpdk.dev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git